Unsure what transmission this is, 700R4? There is a throttle valve or kickdown cable present, and it is definitly an overdrive, behind a 4.3L.

If the vehicle is driven above 50mph, the tcase ends up coated with ATF on the driver side, near the front driveshaft yoke, while the transmission stays dry. The ATF level in the transmission does drop.

We do see a servo cover there, but it doesnt look like an obvious leak there. Because it only happens when driving at speed, everything blows back.

Any thoughts on this? Would this meet the symptom of a tranny output shaft seal leaking? Something about the vacuum lines on top of the tcase?? we've been researching this a bit, but are unsure on where to start..

Any suggestions would be appreciated.. The vehicle does run fine, all shifts are proper..

Thank you!

 

There isn't an out put seal on the back of the transmission, but rather, an input seal on the front of the transfer case. It is possible that the vacuum switch has failed and is puking transmission fluid out somehow. It is cheap enough to replace.

 

sounds like either the vacuum switch or the front driveshaft output is leaking. If your t-case input seal is bad your tranny is draining into the t-case and overfiling it, it has to go somewhere, and out the weakest link.

Is your tranny low on fluid?
Take out the top plug on the back side of the t-case, if you get more then a couple dribbles you got a input seal leak. $5 part.